beneath the table to the abstract. Use the Word Count cmd under Utilites menu for counting Significance Infection with simian type D retrovirus (SRV/D) is endemic in many populations of macaques. SRV/D is a significant pathogen in macaque colonies, being the etiologic agent of one form of simian acquired immune deficiency disease. In addition to its importance from an animal health perspective, SRV/D infection may also represent a significant confounding variable in the interpretation of research results obtained using macaques as experimental subjects. These studies have been undertaken in recognition of the importance of establishing and maintaining breeding colonies of macaques free of SRV/D infection. Objectives The objectives of this research are 1) to develop enhanced serologic and virologic diagnostic tests for SRV/D infection and 2) develop a SRV DNA vaccine for use in highly endemic populations. The ultimate objective is to employ these improved assays and prevention strategies in support of the NCRR-sponsored SPF rhesus macaque development program, and other independent efforts to eliminate SRV infection in macaques used in biomedical research. Results We have successfully developed and validated a nested RT-PCR for the detection of SRV RNA in macaque plasma, and other cell-free media. Additionally, we have developed and validated nested-PCR protocols for use with pooled peripheral blood samples from macaques. We have consistently detected a single positive sample pooled with up to 5 negative samples. While not appropriate for all screening situations, under specific circumstances pooled sample screening can greatly increase the cost-efficiency of PCR testing. This would be especially useful and cost-effective in validating the continued SRV-negative status of established SPF colonies. We have successfully made a prototype SRV DNA vaccine - plasmid construct containing gp20/gp70 env region of SRV/D-2 viral genome - and successfully transfected a mammalian cell line (COS). Expression of viral antigens in transfected cells is currently being evaluated. Future Directions We will continue to evaluate the limits and utility of pooled sample testing of macaque blood to determine the optimal pool size. In addition, we will continue development of the DNA vaccine against SRV. We will initially test the construct for immunogenicity in mice. If successful, the efficacy will be evaluated in immunization studies in macaques with experimental viral challenge. Such a vaccine would be relatively inexpensive to produce and if effective, could theoretically eliminate viral transmission in highly endemic populations, where test and removal procedures are not feasible. Preliminary discussions are in progress to arrange to "field test " our vaccine in a large, free-ranging population of macaques in which SRV/D infection is endemic. KEY WORDS SRV/D, retrovirus, macaque, diagnosis, PCR, SPF, vaccine FUNDING NIH Grant RR00169